Re: Triggers on columns

Hi,

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> By the way, I completely agree that it would be useful to have a way
> to suppress triggers from firing when no columns were actually
> modified.

http://www.postgresql.org/docs/8.4/static/functions-trigger.html

Currently PostgreSQL provides one built in trigger function,
suppress_redundant_updates_trigger, which will prevent any update that
does not actually change the data in the row from taking place, in
contrast to the normal behaviour which always performs the update
regardless of whether or not the data has changed. (This normal
behaviour makes updates run faster, since no checking is required, and
is also useful in certain cases.)

...

The suppress_redundant_updates_trigger function can be added to a table like this:

CREATE TRIGGER z_min_update
BEFORE UPDATE ON tablename
FOR EACH ROW EXECUTE PROCEDURE suppress_redundant_updates_trigger();

Regards,
--
dim